Dual Gilbert Cell Mixer with Offset Cancellation

Abstract

An electronic device includes a first mixer portion having a first stage and a second stage, and a second mixer portion having a first stage and a second stage. A first electrical path is coupled to the first mixer portion and the second mixer portion, and a second electrical path is coupled to the first mixer portion and the second mixer portion. The first mixer portion is adapted to receive a first input signal on the first stage and a second input signal on the second stage. The second mixer portion is adapted to receive the second input signal on the first stage and the first input signal on the second stage.

Description

[0001]This application is a continuation of co-pending International Application No. PCT / IB2007 / 053138, filed Aug. 8, 2007, which designated the United States and was published in English, and which claims priority to European Application No. 06118709.2 filed Aug. 10, 2006, both of which applications are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to an electronic device including a mixer for mixing two input signals.BACKGROUND[0003]Frequency translation in electronic data processing systems is usually performed by devices known as mixers. There are various different architectures for mixing two signals for modulation purposes covering simple single ended, single balanced mixers, and double balanced mixers providing, e.g., improved isolation from the local oscillator (LO). The most popular double balanced mixer used in radio frequency integrated circuit designs is the Gilbert cell mixer. The Gilbert cell is basically a cross-couple diff...

AI Technical Summary

Benefits of technology

[0007]In one aspect, the present invention provides an electronic device for a mixer circuit for processing input signals providing enhanced quality of the output signals. In another aspect, the present invention improves mixing of signals having relatively steep slopes, more specifically the mixing of square waves.

[0010]According to another aspect of the invention the second stages of the first and second mixer portions provide substantially the same capacitive load to the respective first stages. Though a considerable effect is already reached if a constant alternating, and exchanging of the electrical paths and the parasitic capacitances or the like is carried out, the effect can be improved if the second stages of the mixer portions are matched. The parasitic capacitors of the second stages provide a considerable capacitive load. Particularly, for Gilbert cell mixers in combination with square waves, the parasitic capacitances of the second stage are constantly loaded via the same load devices, i.e. via the same electrical path. According to this aspect of the present invention, the second stage of the two mixer portions are matched with respect to each other. Accordingly, not only the electrical properties of the active devices are matched, but the parasitic effects are considered separately. As the charging and discharging of the parasitic capacitances of both of the second stages occurs alternately via the two paths, the error introduced by mismatch is additionally reduced. Another positive effect can be achieved, if according to still another aspect of the invention the first and second mixer portions and the first and second electrical paths are matched with respect to their electrical properties. This aspect relates to all electrical properties rather than to the non-ideal electronic components.

[0014]According to an aspect of the invention the first electrical path and the second electrical path of the electronic device each provide an output. Between the two outputs, the electronic device provides a differential output signal. The differential or symmetric output signal is more robust against noise and offsets.

Problems solved by technology

Such a single mixer device provides parasitic capacitances, resistors, etc, due to non-ideal properties of the electronic devices.

The parasitic capacitors of the second stages provide a considerable capacitive load.

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